Thin slab nozzle for distributing high mass flow rates

Abstract

A thin slab nozzle contains a central bore extending downstream along longitudinal axis X1 from an inlet orifice at an upstream end. The central bore comprises an upstream bore portion with a height Ha, in communication with a converging bore portion of height He, in communication with a thin bore portion of height Hf ending at the upstream end of a divider, and first and second front ports separated from one another by the divider and coupled to the central bore portion at least partially at the converging bore portion. X2 is a transverse axis, normal to X1, along which the nozzle becomes thinner in a downstream portion. In a section of the thin slab nozzle along a symmetry plane Π1 defined by X1 and by X2, the bore wall of the converging bore portion is curved at all points, and Hf/He≤1.

What is claimed is: 
     
       1. Thin slab nozzle for casting thin slabs made of metal, said thin slab nozzle having a geometry symmetrical with respect to a first symmetry plane Π 1  defined by a longitudinal axis X 1  and a first transverse axis X 2  normal to said longitudinal axis X 1 , and symmetrical with respect to a second symmetry plane Π 2  defined by the longitudinal axis X 1 , and a second transverse axis X 3  normal to both the longitudinal axis X 1  and said first transverse axis X 2 , said thin slab nozzle extending along said longitudinal axis X 1  from:
 an inlet portion, located at an upstream end of the thin slab nozzle and comprising an inlet orifice oriented perpendicularly to the longitudinal axis X 1  to 
 an outlet diffusing portion located at a downstream end of the thin slab nozzle and comprising first and second outlet port orifices, said outlet diffusing portion having a nozzle width, measured along the second transverse axis X 3 , which is at least three times larger than a nozzle breadth of the outlet diffusing portion measured along the first transverse axis X 2 , and comprising a connecting portion connecting the inlet portion and the outlet diffusing portion, said thin slab nozzle further comprising: 
 a central bore defined by a bore wall and opening at said inlet orifice and extending therefrom along the longitudinal axis X 1  until it is closed at an upstream end of a divider, said central bore comprising: 
 an upstream bore portion comprising the inlet orifice and extending over a height Ha and, adjacent thereto, forming an upstream boundary with 
 a converging bore portion of height He located in the connecting portion of the thin slab nozzle, and adjacent thereto 
 a thin bore portion of height Hf located in the diffusing portion of the thin slab nozzle and ending at the level of the upstream end of said divider, 
 first and second front ports separated from one another by the divider and extending parallel to said second symmetry plane Π 2 , said first and second front ports extending from first and second port inlets opening at least partially on two opposite walls of the converging bore portion, to said first and second outlet port orifices, said first and second front ports having a width W 51 , measured along the first transverse axis X 2 , which is always smaller than a width D 2 (X 1 ), of the upstream bore portion measured along the first transverse axis X 2 , 
 
       wherein, in a section of the thin slab nozzle along the first symmetry plane Π 1 , a geometry of the wall of the central bore is characterized as follows:
 the bore wall of the upstream bore portion is substantially straight over at least 90% of the height Ha of the upstream bore portion (excluding the region of the inlet orifice), 
 the bore wall of the converging bore portion is curved at all points, and 
 the ratio of the height Hf of the thin bore portion to the height He of the converging portion is not more than 1, Hf/He≤1. 
 
     
     
       2. Thin slab nozzle according to  claim 1 , wherein a total cross-sectional area A(X 1 ) measured on planes Π 3  normal to the longitudinal axis X 1  of both the central bore and the first and second front ports is characterized in that a relative variation, ΔA(X 1 )/Aa=|Aa−A (X 1 )|/Aa, of the total cross-sectional area A(X 1 ) with respect to the total cross-sectional area Aa at the upstream boundary is not greater than 15%, for any plane Π 3  intersecting the longitudinal axis X 1 , from the upstream boundary down to 70% of the height He of the converging bore portion. 
     
     
       3. Thin slab nozzle according to  claim 1 , wherein the converging bore portion is further divided into two bore portions:
 an end bore portion of height Hc and 
 a transition bore portion of height Hb comprised between and adjacent to the upstream bore portion and the end bore portion, thus forming at one end a transition boundary with the end bore portion and, at the other end the upstream boundary with the upstream bore portion, 
 
       and wherein in a section of the thin slab nozzle along the first symmetry plane Π 1  the geometry of the wall of the converging bore portion is characterized as follows:
 a radius of curvature ρc 1 , where measured on a section of the thin slab nozzle along the first symmetry plane Π 1  at any point of the bore wall of the end bore portion is not greater than half of a width D 2   a  of the central bore at the upstream boundary, ρc 1 ≤½ D 2   a;    
 a radius of curvature ρb 1 , where measured on a section of the thin slab nozzle along the first symmetry plane Π 1  at any point of the bore wall of the transition bore portion is greater than half of said width D 2   a  and greater than or equal to 5×ρc 1  and less than or equal to 50×D 2   a ; and, 
 a height ratio, Hb/Hc, of the transition bore portion to the end bore portion is equal to or greater than 3 and less than or equal to 12. 
 
     
     
       4. Thin slab nozzle according to  claim 3 , wherein the geometry of the nozzle contains a feature selected from the group consisting of:
 (a) the radius of curvature ρb 1  is constant at any point of the bore wall of the transition bore portion and (b) the radius of curvature ρc 1  is constant at any point of the bore wall of the end bore portion. 
 
     
     
       5. Thin slab nozzle according to  claim 4 , wherein, excluding the first and second port inlets, the radii of curvature and the height ratios of the bore wall of the converging bore portion, transition bore portion and end bore portion defined with respect to a section of the thin slab nozzle along the first symmetry plane Π 1 , apply also to a section of the thin slab nozzle along the second symmetry plane Π 2 . 
     
     
       6. Thin slab nozzle according to  claim 1 , wherein the converging bore portion of the central bore, excluding the first and second port inlets, has an elliptical or circular cross-section along a plane Π 3 , normal to the longitudinal axis X 1 , having principal diameters, D 2 (X 1 ), D 3 (X 1 ), along the first transverse axis X 2  and second transverse axis X 3  respectively, whose dimensions evolve along the longitudinal axis X 1 , such that a ratio D 2 (X 1 )/D 3 (X 1 ) remains constant, with D 2 (X 1 )≤D 3 (X 1 ). 
     
     
       7. Thin slab nozzle according to  claim 5 , wherein the converging bore portion ( 50   e ) has a geometry of revolution about the longitudinal axis X 1 , excluding the first and second port inlets ( 51   u ). 
     
     
       8. Thin slab nozzle according to  claim 1 , wherein a distance between the upstream end of the thin slab nozzle and the upstream end of the first and second port inlets is comprised within the height Ha of the upstream bore portion ±7% and wherein on the second symmetry plane Π 2 , the first and second front ports meet the central bore at an angle α, with respect to the longitudinal axis X 1 , equal to or greater than 5° and equal to or less than 45°. 
     
     
       9. Thin slab nozzle according to  claim 1 , wherein the geometry in a section along the second symmetry plane Π 2 , of the walls of the divider in contact with the first and second front ports is characterized by both walls extending from the upstream end of the divider to the downstream end of the thin slab nozzle along the longitudinal axis X 1 , by first diverging until the divider reaches its maximum width and then converging until they reach the downstream end of the thin slab nozzle. 
     
     
       10. Thin slab nozzle according to  claim 1 , wherein a height Hd of the divider is at least twice as much as the height He of the converging bore portion, Hd≥He. 
     
     
       11. Thin slab nozzle according to  claim 1 , wherein a ratio W 51 /D 2   a , of the width W 51  of the first and second front ports along the first transverse axis X 2 , to the width D 2   a  along the first transverse axis X 2  of the central bore at the upstream boundary is equal to or greater than 15% and equal to or less than 40%. 
     
     
       12. Thin slab nozzle according to  claim 3 , wherein a ratio D 2   b /D 2   a , of a width D 2   b , along the first transverse axis X 2 , of the central bore at the transition boundary to the width D 2   a , along the first transverse axis X 2  of the central bore at the upstream boundary is equal to or greater than 65% and equal to or less than 85%. 
     
     
       13. Thin slab nozzle according to  claim 1 , wherein a derivative dA/dX 1  in the converging bore portion of a total cross-sectional area A on any plane n 3  normal to the longitudinal axis X 1  with respect to a position of said plane n 3  on the longitudinal axis X 1  is never greater than 0, dA/dX 1 ≤0. 
     
     
       14. Thin slab nozzle according to  claim 1 , wherein,
 the ratio of the height Hf of the thin bore portion to the height He of the converging bore portion is not more than 50%, and 
 the ratio of the height Hf of the thin bore portion to the total height of the central bore is not more than 15%.